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No. 752,634. l PATENTED FEB. 16, 1904. E. W. YOUNG.

COMMUTATOR FOR DYNAMO ELECTRIC MACHINES.

APPLICATION FILED MAY 22, 1903. RENEWED JAN. 9, 1904. N0 MODEL.

UNITED STATES Patented February 16, 1904.

PATENT OEEIcE.

FREDERICK WM. YOUNG, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO CROCKER-WHEELER COMPANY, OF AMPERE, NEl/V JERSEY, A CORPORA- TION OF NEW JERSEY.

CONINIUTATOR FOR DYNAlVlO-ELECTRIC MACHINES.

SPECIFICATION forming part of Letters Patent No. 752,634, dated February 16, 1904.

Application filed May 22, 1903. Renewed January 9, 1904. Serial No. 188,409. (No model.)

To all whom it may concern:

Be it known that I, FREDERICK WILLIAM YOUNG., a citizen of the United States of America, and a resident of East Orange, county of Essex, and State of New Jersey, have invented certain new and useful Improvements in Oommutators for Dynamo-Electric Machines, of which the following is a specification.

My invention relates to a commutator con- Io sisting of composite commutator-bars each made of a metallic bar, usually of copper, and a carbon bar, which are electrically connected, preferably by direct contact, and arranged with respectv to the direction of rotation of the commutator, so that contact of the carbon bar with any brush will be established before contact is broken at the connected copper bar and circuits will be completely broken only at the carbon bars as these bars pass from under the brushes.

One object of the invention is to eect a shifting of the connection of each coil of the armature and terminal of the .machine with which it may be connected through the cop- 2 5 per bar of a composite commutator-bar and a brush to a path of very much higher resistance through the carbon bar before opening the circuit and arresting the current in the coil, thereby avoiding the complete breaking of circuits on the copper bars and consequent burning of the copper bars and sparking at the brushes.

A second object of the invention is to provide a non-fusible material in the commuta- 3 5 tor, between which and the brushes the actual opening of the short circuit caused by the bridging of contiguous commutator-bars will take place.

A third object of the invention is to provide a composite commutator-bar consisting of a high-resistance bar alongside of each copper bar the material of which has such a high speciiic resistance that the desired actual resistance can be obtained, although there is direct contact between one side of the high-resistance bar and the copper bar with which it is in electrical connection.

A fourth object of the invention is to provide in a commutator a composite commutator-bar comprising a copper bar and in con- 5o junction therewith a high-resistance bar the material of which has such a high specific resistance that it may be of such thickness without sacriiice of necessary resistance that the time required for the brush to traverse the surface of the high-resistance bar after breaking contact with the connected commutatorbar will be sufficient for the self-induced eurrent to die out in the connected armature-coil.

A fifth object of the invention is to provide 6o in a commutator, in conjunction with each mica insulation between the copper commutator-bars, a non-ductile substance of high resistance and of such thickness that, in conjunction with the mica insulation, it will not be entirely overlapped by the turnings of ductile copper which are partially detached in the turning off of the commutator and left hanging from the edges of the copper bars, thereby causing short circuits of the arma- 7o ture-coils in case the bars are too close together.

A sixth object of the invention is to provide in a commutator, in conjunction with each mica insulation between the copper commutator-bars, an infusible substance of high resistance and of such thickness that, in conjunction with the mica insulation, it will space the contiguous copper bars too far apart to be bridged by any particles of copper liberated by sparking, which might otherwise connect contiguous copper bars if they were closer together and occasion partial short circuits, which are known as ring-fire.

A seventh object of the invention is to pro- 8 5 vide a commutator in which a considerable proportion of the commutator-bars is of a material of less speciiic gravity than copper or other metal, thereby reducing the centrifugal force acting on the bars, and hence reducing the liability to bursting of the commutator, and thereby permitting higher speeds.

An eighth object of the invention is to provide a commutator in which a considerable proportion of the commutator-bars is of a material of less cost than copper or other metals suitable for commutator-bars, thereby reducing the total cost of the commutator.

A ninth object of the invention is to provide a commutator and brushes contacting therewith of such construction that the actual breaking of circuits will be between contact parts both of which are of carbon.

In the accompanying sheet of drawings, which forms a part of this specification, Figure l shows a commutator for a dynamo-electric generator or motor constructed in accordance with my invention in conjunction with the brushes therefor, the machine being intended to run in either direction. Fig. 2 shows a vertical section through the axis of the commutator, together with a portion of the armature of the dynamo-electric machine.

The commutator is composed of the usual number of copper bars c, which are connected to the coils a of the armature in the usual manner. The bars are clamped in the usual supporting-ring r and are suitably insulated from the ring by mica packing p. Each bar, however, is narrower than is usual, the necessary width being made up by an auxiliary carbon bar or bars Z d' on one or both sides and in electrical connection with the copper bar, thereby forming, with the copper bar, a composite commutator-bar. It is essential that the carbon should be on the sides of the copper bars which, taking into account the direction of rotation, are the last to pass out from under each of the brushes and hence are on the leaving sides of the copper bars, so that at the moment when contact is broken between any copper bar and a contacting brush the current which may be flowing between the copper bar and brush can continue to iiow between the brush and the higher-resistance earbon bar and be choked thereby. The current which is thus shifted is mainly the current across a short circuit between contiguous composite eommutator-bars. This is an induced current in the armature-coil, the terminals of which are connected to the short-circuited commutator-bars. This induced current may be very large, although it is of brief duration, lasting usually about one thousandth part of a second, with the high-resistance carbon bar in the circuit. The width of face of the carbon bar, which is about an eighth of an inchi at the usual commutator speed, is such that about this period of time will elapse after the circuit is shifted to the carbon bar until it is opened at the carbon bar. Hence the commutator-bars leave the brushes practically without sparking'.

The machine illustrated is intended for both directions of rotation. Each composite conimutator-bar consists of a copper bar c, with a carbon bar d in contact therewith on one side and a carbon bar d in contact with the copper bar on the opposite side. The composite commutator-bars are separated by mica strips m, and this insulation between contiguous commutator-bars is between the carbon bar Z of one composite bar and the carbon bar CZ of the other composite bar. For counter-clockwise rotation of the commutator the carbon bars el serve to choke and extinguish the induced currents and force the current generated in the armature out into the line. For clockwise rotation the carbon bars ,Z serve the same purpose. For either direction of rotation the added thickness of carbon between the copper bars of contiguous composite bars reduces the danger of short-circuit by the turnings of the ductile copper which are partially detached in turning ol'l" the commutator or by the detached particles of copper liberated by sparking. It also reduces the weight of the commutator, cuts down the centrifugal force, thereby permitting higher speed, and the reduction in the amount of copper lessens the cost.

Carbon has heretofore been regarded as a substance which wears away with such rapidity when subjected to friction that it would seem suited for use only under conditions where it can be readily renewed; but it has been found that when incorporated in a commutator the wear is extremely slight, owing to the protection afforded by the adjoining' copper bars and mica strips, which prevent the wearing away of the carbon bars below the surface of the copper bars and the edges of the mica.

The objects of this invention above enumerated are attained by the use of carbon as a material for the auxiliary bars of the composite commutator-bars in a manner that is not possible with any metal, owing to the extremely high specific resistance of carbon as compared with all available metals and its absolute infusibility. The specilic resistance of carbon compared with copper is from two thousand five hundred to five thousand times, and as compared with German silver, the metal of highest resistance which is available in electrical work, it is from two hundred to four hundred times.

rlhe employment of any particular metal for the low-resistance bars of the commutator is not essential to this invention, although these bars are usually referred to as copper bars, since copper is the usual material employed in commutator construction, and the employment of any particular insulating substance between the composite bars is not essential to the invention, although mica is usually referred to, since it is the insulating substance generally employed.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

l. The combination with a brush, of a commutator with composite commutator bars, each consisting of ametal contact-bar with a carbon contact-bar adjoining the leaving edge in electric contact with the metal contact-bar, substantially as described.

IOO

2. The combination With a brush, of a commutator with composite commutator bars, each consisting of a metal contact-bar with a carbon contact-bar adjoining the leaving edge and in direct contact with the metal contactbar, substantially as described.

3. The combination With a brush, of a commutator With composite commutator bars, each consisting of a metal contact-bar with carbon contact-bars adjoining botli edges and in electric contact with the metal contact-bar, substantially as described.

4. The combination with a brush, of a commutator With composite commutator bars, each consisting of a metal contact-bar With carbon contact-bars adjoining both edges and in direct contact with the metal contact-bar, f 

